Ce-TiO2 nanoparticles with surface-confined Ce3+/Ce4+ redox pairs for rapid sunlight-driven elimination of organic contaminants from water

Industrial discharge of organic pollutants poses a severe threat to human health and aquatic life. Elimination of these pollutants from drinking and wastewater is imperative for a sustainable environment. To address this issue, pure and Ce³⁺-doped TiO₂ nanoparticles are designed with stable tetragonal (anatase) lattices by a low-temperature sol–gel process. The spectroscopic and structural analyses reveal the formation of TiO₂ and Ce-TiO₂ nanocrystals with controlled crystallite size (3–6 nm), high surface areas, and varying surface chemistry. The effect of calcination (thermal (Δ) treatment at 450 °C) on the structure and photocatalytic performance of ΔTiO₂ and ΔCe-TiO₂ nanoparticles is also investigated. Simultaneous photocatalysis experiments over a 90-min exposure to natural sunlight show 240 % and 191 % improved elimination of methylene blue (MB), an organic pollutant, by Ce-TiO₂ and ΔCe-TiO₂ nanoparticles compared to their pure TiO₂ analogs. Also, Ce-TiO₂ and ΔCe-TiO₂ nanoparticles exhibit 326 % and 229 % faster kinetics for the photocatalytic elimination of MB primarily due to the surface-confinement of Ce³⁺ in Ce-TiO₂ nanocrystals, where Ce³⁺ ions play a dual role as reducing agent for adsorbed oxygen species and electron trap sites via Ce³⁺/Ce⁴⁺ interconversion. The mechanism of photocatalytic redox reactions is discussed. The study elaborates on the role of Ce-TiO₂ nanoparticles as an effective photocatalyst for the elimination of organic pollutants in wastewater.